In March 2020, just as Covid-19 was turning the world upside down, I found myself in Dallas, Texas, in the room where Lee Harvey Oswald had shot and killed President Kennedy almost 60 years earlier. The former Texas School Book Depository has been turned into a museum about Kennedy’s life and death, offering a sober, measured account of the events of November 1963. On the quiet streets outside the museum, however, I encountered a few street stalls, whose occupants were peddling a very different view of the assassination. Here all manner of conspiracies were given full voice, ones that I’m sure you’ll all be familiar with: the FBI, or the CIA, or the mafia, or the Soviets, or the Cubans, or some combination of them had undoubtedly orchestrated the killing…